Thalidomide analogue CC-3052 reduces HIV+ neutrophil apoptosis in vitro

Recent developments of phosphodiesterase inhibitors: Clinical trials, emerging indications and novel molecules

The phosphodiesterase (PDE) enzymes, key regulator of the cyclic nucleotide signal transduction system, are long-established as attractive therapeutic targets. During investigation of trends within clinical trials, we have identified a particularly high number of clinical trials involving PDE inhibitors, prompting us to further evaluate the current status of this class of therapeutic agents. In total, we have identified 87 agents with PDE-inhibiting capacity, of which 85 interact with PDE enzymes as primary target. We provide an overview of the clinical drug development with focus on the current clinical uses, novel molecules and indications, highlighting relevant clinical studies. We found that the bulk of current clinical uses for this class of therapeutic agents are chronic obstructive pulmonary disease (COPD), vascular and cardiovascular disorders and inflammatory skin conditions. In COPD, particularly, PDE inhibitors are characterised by the compliance-limiting adverse reactions. We discuss efforts directed to appropriately adjusting the dose regimens and conducting structure-activity relationship studies to determine the effect of structural features on safety profile. The ongoing development predominantly concentrates on central nervous system diseases, such as schizophrenia, Alzheimer's disease, Parkinson's disease and fragile X syndrome; notable advancements are being also made in mycobacterial infections, HIV and Duchenne muscular dystrophy. Our analysis predicts the diversification of PDE inhibitors' will continue to grow thanks to the molecules in preclinical development and the ongoing research involving drugs in clinical development.

Phosphodiesterase-4 inhibition alters gene expression and improves isoniazid-mediated clearance of Mycobacterium tuberculosis in rabbit lungs

Tuberculosis (TB) treatment is hampered by the long duration of antibiotic therapy required to achieve cure. This indolent response has been partly attributed to the ability of subpopulations of less metabolically active Mycobacterium tuberculosis (Mtb) to withstand killing by current anti-TB drugs. We have used immune modulation with a phosphodiesterase-4 (PDE4) inhibitor, CC-3052, that reduces tumor necrosis factor alpha (TNF-α) production by increasing intracellular cAMP in macrophages, to examine the crosstalk between host and pathogen in rabbits with pulmonary TB during treatment with isoniazid (INH). Based on DNA microarray, changes in host gene expression during CC-3052 treatment of Mtb infected rabbits support a link between PDE4 inhibition and specific down-regulation of the innate immune response. The overall pattern of host gene expression in the lungs of infected rabbits treated with CC-3052, compared to untreated rabbits, was similar to that described in vitro in resting Mtb infected macrophages, suggesting suboptimal macrophage activation. These alterations in host immunity were associated with corresponding down-regulation of a number of Mtb genes that have been associated with a metabolic shift towards dormancy. Moreover, treatment with CC-3052 and INH resulted in reduced expression of those genes associated with the bacterial response to INH. Importantly, CC-3052 treatment of infected rabbits was associated with reduced ability of Mtb to withstand INH killing, shown by improved bacillary clearance, from the lungs of co-treated animals compared to rabbits treated with INH alone. The results of our study suggest that changes in Mtb gene expression, in response to changes in the host immune response, can alter the responsiveness of the bacteria to antimicrobial agents. These findings provide a basis for exploring the potential use of adjunctive immune modulation with PDE4 inhibitors to enhance the efficacy of existing anti-TB treatment.

Tuberculosis (TB) caused by Mycobacterium tuberculosis (Mtb) is a leading infectious cause of morbidity and mortality. Although current antibiotic regimens can cure TB, treatment requires at least six months for completion. Recent studies indicate that bacteria in a less metabolically active state are less responsive to antibiotic killing and suggest that this may partly explain the long duration required for TB treatment. In this study, using a rabbit model of pulmonary TB, we show that immune modulation of Mtb infected animals with CC-3052, a phosphodiesterase-4 (PDE4) inhibitor that reduces tumor necrosis factor alpha (TNF-α) production by increasing intracellular cAMP levels, resulted in the down-regulation of host genes involved in the innate immune response. Bacteria from the lungs of CC-3052 treated rabbits displayed differential expression of those genes associated with stress responses. In addition, co-treatment of INH with CC-3052 abolished the INH-induced Mtb gene expression in the infected rabbits. Importantly, bacillary clearance from the lungs of rabbits co-treated with CC-3052 and INH was improved over that in animals treated with INH alone. The results of this study provide a basis for novel use of immune modulation to improve the efficacy of antibiotic therapy and to shorten the duration of TB treatment.

Phosphodiesterase 4 inhibition reduces innate immunity and improves isoniazid clearance of Mycobacterium tuberculosis in the lungs of infected mice

Tuberculosis (TB) caused by Mycobacterium tuberculosis (Mtb) is one of the leading infectious disease causes of morbidity and mortality worldwide. Though current antibiotic regimens can cure the disease, treatment requires at least six months of drug therapy. One reason for the long duration of therapy is that the currently available TB drugs were selected for their ability to kill replicating organisms and are less effective against subpopulations of non-replicating persistent bacilli. Evidence from in vitro models of Mtb growth and mouse infection studies suggests that host immunity may provide some of the environmental cues that drive Mtb towards non-replicating persistence. We hypothesized that selective modulation of the host immune response to modify the environmental pressure on the bacilli may result in better bacterial clearance during TB treatment. For this proof of principal study, we compared bacillary clearance from the lungs of Mtb-infected mice treated with the anti-TB drug isoniazid (INH) in the presence and absence of an immunomodulatory phosphodiesterase 4 inhibitor (PDE4i), CC-3052. The effects of CC-3052 on host global gene expression, induction of cytokines, and T cell activation in the lungs of infected mice were evaluated. We show that CC-3052 modulates the innate immune response without causing generalized immune suppression. Immune modulation combined with INH treatment improved bacillary clearance and resulted in smaller granulomas and less lung pathology, compared to treatment with INH alone. This novel strategy of combining anti-TB drugs with an immune modulating molecule, if applied appropriately to patients, may shorten the duration of TB treatment and improve clinical outcome.

Thalidomide and its analogues have distinct and opposing effects on TNF-alpha and TNFR2 during co-stimulation of both CD4(+) and CD8(+) T cells

Thalidomide (Thd) is clinically useful in a number of conditions where its efficacy is probably related to its anti-TNF-alpha activity. More recently, Thd has also been shown to co-stimulate T cells and second generation co-stimulatory (IMiD trade mark ) analogues are currently being assessed in the treatment of cancer patients. However, in contrast to their known suppressive effects during inflammatory stimuli, the effects of Thd/IMiDs on TNF-alpha and TNF receptors (TNFRs) during T cell co-stimulation are not known. We sought to determine the effect of Thd, two clinically relevant IMiDs (CC-4047, ACTIMID trade mark and CC-5013, REVIMID trade mark ) and a non-stimulatory SelCID analogue (CC-3052) on TNF-alpha production and on the expression and shedding of TNFRs during co-stimulation. We found that co-stimulation of PBMC with Thd/IMiDs, but not CC-3052, prevented alphaCD3-induced T cell surface expression of TNFR2 and thereby reduced soluble TNFR2 (sTNFR2) levels. However, there was no effect on total (surface/intracellular) TNFR2 protein expression, suggesting inhibition of trafficking to the cell membrane. The extent of co-stimulation by Thd/IMiDs (assessed by CD69/CD25 expression and IL-2/sIL-2Ralpha production) was similar for CD4+ and CD8+ T lymphocytes and correlated with TNFR2 inhibition. Co-stimulation, but not the early inhibitory effect on TNFR2, was IL-2-dependent and led to increased TNF-alpha production by both CD4+ and CD8+ T lymphocytes. The clinical relevance of this observation was confirmed by the elevation of serum TNF-alpha during REVIMID trade mark treatment of patients with advanced cancer. Together, these results suggest a possible role for TNF-mediated events during co-stimulation and contrast with the TNF inhibitory effects of Thd and its analogues during inflammatory stimuli.

Thalidomide in cancer treatment: a potential role in the elderly?

There is increased interest in the treatment of cancer with thalidomide because of its antiangiogenic, immunomodulating and sedative effects. In animal models, the antitumour activity of thalidomide is dependent on the species, route of administration and coadministration of other drugs. For example, thalidomide has shown antitumour effects as a single agent in rabbits, but not in mice. In addition, the antitumour effects of the conventional cytotoxic drug cyclophosphamide and the tumour necrosis factor inducer 5,6-dimethylxanthenone-4-acetic acid (DMXAA) were found to be potentiated by thalidomide in mice bearing colon 38 adenocarcinoma tumours. Further studies have revealed that thalidomide upregulates intratumoral production of tumour necrosis factor-alpha 10-fold over that induced by DMXAA alone. Coadministration of thalidomide also significantly reduced the plasma clearance of DMXAA and cyclophosphamide. All these effects of thalidomide may contribute to the enhanced antitumour activity. Recent clinical trials of thalidomide have indicated that it has minimal anticancer activity for most patients with solid tumours when used as a single agent, although it was well tolerated. However, improved responses have been reported in patients with multiple myeloma. Palliative effects of thalidomide on cancer-related symptoms have also been observed, especially for geriatric patients with prostate cancer. Thalidomide also eliminates the dose-limiting gastrointestinal toxic effects of irinotecan. There is preliminary evidence indicating that the clearance of thalidomide may be reduced in the elderly. The exact role of thalidomide in the treatment of cancer and cancer cachexia in the elderly remains to be elucidated. However, it may have some value as part of a multimodality anticancer therapy, rather than as a single agent.

Protective antitumor immunity induced by a costimulatory thalidomide analog in conjunction with whole tumor cell vaccination is mediated by increased Th1-type immunity

Thalidomide and its novel T cell costimulatory analogs (immunomodulatory drugs) are currently being assessed in the treatment of patients with advanced cancer. However, neither tumor-specific T cell costimulation nor effective antitumor activity has been demonstrated in vivo. In this study, we assessed the ability of an immunomodulatory drug (CC-4047/ACTIMID) to prime a tumor-specific immune response following tumor cell vaccination. We found that the presence of CC-4047 during the priming phase strongly enhanced antitumor immunity in the vaccinated group, and this correlated with protection from subsequent live tumor challenge. Protection was associated with tumor-specific production of IFN-gamma and was still observed following a second challenge with live tumor cells 60 days later. Furthermore, CD8(+) and CD4(+) splenocyte fractions from treated groups secreted increased IFN-gamma and IL-2 in response to tumor cells in vitro. Coculture of naive splenocytes with anti-CD3 mAb in the presence of CC-4047 directly costimulated T cells and increased Th1-type cytokines. Our results are the first to demonstrate that a costimulatory thalidomide analog can prime protective, long-lasting, tumor-specific, Th1-type responses in vivo and further support their ongoing clinical development as novel anti-cancer agents.